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For magnet lovers...

Discussion in 'Electronic Design' started by Greysky, Jun 22, 2004.

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  1. Greysky

    Greysky Guest

    ever since I was a child, magnets have held a fascination for me. I've been
    collecting them ever since. It used to be that you could always scrounge
    loudspeakers for Alnico magnets. Then when the newer ceramic magnets began
    to be incorporated into loudspeakers, it became a challenge to remove them
    from their enclosures without breaking them. Now, I have to admit, I am
    having a ball collecting the new 'super magnets' - like the ones inside hard
    drives. There are also cool cylindrical magnets that you can get from inside
    the heads of VHS machines. My question is does anyone know of other sources
    either for Neodymium 'duper magnets', or strong ceramic magnets that I may
    be missing out on? Magnets like these come closest to being perpetual motion
    machines we have yet to make, and I'd hate to have some just wind up into
    the trash because I didn't know they were there :)

  2. There is a big magnetic iron core if you dig deep enough.
    There are stars with an extremly strong magnetic field,
    very very strong.
    We need a composite (non metal) spaceship.
  3. Boris Mohar

    Boris Mohar Guest

    Take apart a hard drive. There is a pail of magnets in the head positioning
    servo. They are very powerful and will pinch your fingers if yo are not


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs
  4. They are magic, aren't they? Have you tried the drop a magnet down a
    copper pipe trick?

    Steve J. Noll | Ventura California |
    | The Used High-Tech Equipment Dealer Directory
    | The Peltier Device Information Site:
  5. Julie

    Julie Guest

    For purchase:

    has a small assortment.

    As you are probably aware, the older the drive, typically the bigger the
    magnets. The largest that I've found were from an old full-height 5 1/4"
    internal 300 MB SCSI drive. Newer drives are a bit disappointing, their
    magnets are getting pretty thin and break easily...
  6. and this..


    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
  7. Steve Nosko

    Steve Nosko Guest

    Now how come I never thought of that one. Know what i'll be doing this
  8. JW

    JW Guest

    I'll bite. What happens?
  9. Rick

    Rick Guest

    I just tried it with a 1/2 inch copper pipe and a 1/4 inch cube magnet.
    Incredible! I did not know it would have that much of an effect!
  10. Tom Bruhns

    Tom Bruhns Guest

    What a great mental image! I was in need of a chuckle today, and you
    came through. Thanks. (BTW, the OP had already mentioned the HD
  11. Paul_Morphy

    Paul_Morphy Guest

    I'm guessing some EMF is induced.

  12. Tim Wescott

    Tim Wescott Guest

    Hey fun! I knew about the effect, but never thought to try it with
    something so mechanically simple. I'm going to have to show the kids now.
  13. Julie

    Julie Guest

  14. Steve Nosko

    Steve Nosko Guest

    Chuckle chuckle...anyone have a silver pipe?

    Steve N, K,9;d, c. i My email has no u's.
  15. Steve Nosko

    Steve Nosko Guest

    ....and... continue with the line of reasoning...

    What does that EMF produce and where?...
  16. Steve

    Steve Guest

    what does it do??
  17. Steve

    Steve Guest

  18. The magnet moving down the pipe induces eddy currents. These eddy
    currents produce an electromagnetic force that resists the movement of the
    magnet (with respect to the pipe) and does so to an extent varying
    directly with the speed at which the magnet is moving. This slows down
    the magnet.

    At least this is what I have heard.

    And aluminum tubes do this also, just not quite as much as copper ones
    do. And I have seen aluminum tube stock.

    Most other metals do this less, but I imagine that iron and lead pipes
    may slow the fall of a close-fitting "rare earth magnet" a little in
    comparison to nonconductive pipes.

    - Don Klipstein ()
  19. Rich Grise

    Rich Grise Guest

    Actually, I think the metaphasic shield gets around that problem.

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